Truck-mounted concrete mixer



J. w. LENDVED 2,696,371

TRUCK-MOUNTED CONCRETE MIXER Dec. 7, 1954 3 Sheets-Sheet 1 Filed Aug. 5, 1951 JOHN W. LENDVED INVENTOR.

BY W Aim Dec. 7, 1954 J. w. LENDVED TRUCK-MOUNTED CONCRETE MIXER s Sheets-Sheet 3 Filed Aug. 5. 1951 F I G. 4.

' FIG.5.

46 JOHN W.LENDVED INVENTOR. 1 BY 77% Mwm ATTORNEY H H S that is especially adapted United States Patent .0

2,696,371 TRUCK-MOUNTED CONCRETE MIXER Application August 3, 19s1,-senal No. 240,141 Claims. Cl. 259161) to concrete mixers or This invention relates, generally,

transit-mixer type for agitators of the truck-mounted or mixing and/or transporting concrete, and more particularly to an improved mobile mixer especially arranged to carry the maximum permissible load of concrete on a motor truck of standard construction.

Heretofore, truck-mounted concrete mixers or transitmixers for mixing or agitating concrete en route to or at the site or" placement have been mounted on commercial motor trucks of standard construction in a position such that the discharge end of the mixer is located at approximately the rear of the truck frame for convenience in discharging the mixed concrete at the back of the truck. Another established characteristic of mixers of previously known construction has been the disposition of the drumrotating mechanism between the mixer drum and the cab of the supporting truck. Under these circumstances the been so shaped and positioned that the weight of the mixer and its load of concrete is carried largely by the rear wheels of the truck, the front wheels ordinarily carrying only some ten to fifteen percent of the loaded mixer weight in addition to their proportionate share of the weight of the truck itself.

For reasons of economy, transit-mixers are preferably mounted on motor trucks of well-known, standard commercial construction having the drivers cab behind the propulsion engine and provided with two front wheels for steering and either two or four rear wheels for driving. This provides the most economical form of transportation, inasmuch as trucks of this type are mass-produced and are extensively used and serviced throughout the country.

In an effort to promote further economy, users of transit-mixers have been adopting larger and larger mixer drums in order that greater loads of concrete can be carried in one haul. However, this desire to reduce costs by carrying heavier loads conflicts with the requirements that maximum limits be placed on the wheel loads of trucks operating over streets and highways.

In recent years studies of highway usage with respect to the relationship between highway deterioration an wheel loads, have indicated that excessive damage to highway surfaces results from subjecting highways to wheel loads that exceed determined safe maximum limits. As a result, governmental authorities have taken steps to protect highways from undue damage throug establishing legal limits on overall truck loads and on the loadings of the several individual truck wheels under various circumstances. In view of the fact that the rear wheels of motor trucks carrying concrete are ordinarily already loaded to the limit, it is not feasible to increase the carrying capacity of a truck mixer by merely increasing the size of the mixer drum, as this would result in wheels of the truck a greater load imposing upon the rear to the highthan can be exerted without excessive injury way.

A general object of the present invention is to provide an improved concrete mixer of the truck-mounted type for mounting on a motor truck of standard construction and is so arranged as to be capable of carrying the maximum load of concrete that can be transported by the truck without imposing on any of the wheels of the truck a load in excess of that which the highway will sustain without undue deterioration.

Another object of the invention is to provide an improved truck mixer for mounting on a standard motor is mass-produced by various p the back of the drivers cab.

when the truck is truck that is especially arranged to effect optimum loading of the several wheels of the truck.

Another object is to provide an improved truckmounted concrete mixer so arranged that the front wheels of the truck will sustain from twenty to thirty percent of the mixer load.

A further object is to provide a truck-mounted concrete mixer in which the mixing drum is so proportioned and its auxiliary elements so arranged that the tapered discharge end of the drum may be disposed above the rear wheels of a standard motor truck in a position adapted for conveniently discharging the mixed concrete while its enlarged forward end is disposed adjacent to the cab of the truck in a position to impose the weight of the drum and its load of concrete sufficiently forward on the truck to effect optimum loading of the several wheels of the truck, all, without increasing the permissible overall dimensions of the mixer or impairing its operating functions.

According to the present invention, an improved concrete mixer of the truck-mounted type is arranged to transport a heavier load of concrete on a standard commercial motor truck by effecting optimum loading of the several wheels of the truck to the limits permitted for use on the highways over which the truck operates. This is accomplished by arranging the improved mixer whereby a larger proportion of the weight of the mixer and its load of concrete is imposed upon the front wheels of the truck, the arrangement being such that all of the wheels of the truck are loaded to full capacity, whereby the maximum possible load of concrete may be carried by the truck without subjecting the highway surface to injurious overloading. For best overall economy in transporting concrete, the improved mixer is especially arranged for use on the usual motor truck of conventional type, which manufacturers and economically serviced throughout the country, thereby providing transportation at the lowest cost. The optimum distribution of load on the truck is attained by so shaping and positioning the mixer drum that the concrete being transported is disposed forwardly on the truck frame close to To provide for discharging manner at the rear of the truck, the axis of the mixing drum is inclined upwardly to the rear, and the drum is made substantially longer than usual and tapers rearwardly to an elevated discharge end that is disposed above the rear wheels of the truck. The forward end of the tapered drum is made as large as possible in order that the load of concrete will tend to be concentrated forwardly therein. To make possible the positioning of the mixing drum as far forward as possible on the truck, the driving mechanism for rotating the drum, which may be either a separate engine or a transmission deriving its power from the truck transmission, is mounted on the mixer frame beneath and operatively connected as hereinafter described, to the elevated rear or discharge end of the drum. The water supply tank for the mixer is preferably mounted ahead of the closed or forward end of the drum in a position to overhang the truck cab. By this improved disposition of the mixer mechanism and improved shape of the mixing drum, a truck-mounted mixer embodying the present invention is adapted to carry a greater load of concrete than was heretofore considered possible on a motor truck of standard construction without exerting excessive wheel-loadings on the roadway being traversed. By mounting the driving mechanism on the mixer frame closely adjacent to the discharge end of the drum, as hereinafter described, misalignment between the drum and its driving element is minimized, for such twisting of the frame as occurs driven does not produce relative movement of these instrumentalities to the extent whichpreviously occurred when the head end of the drum was driven from an adjacent power source.

The foregoing and other objects of this invention will become more fully apparent as the following detailed description of an exemplary embodiment thereof is read in conjunction with the accompanying illustrative drawings wherein:

Figure the mixer in the usual 1 is a somewhat diagrammatic view in left side elevation of a truck-mounted concrete mixer embodying the present invention shown installed on a representative motor truck of standard commercial construction;

Fig. 2 is an enlarged fragmentary detail view of the water tank supporting frame element shown in Fig. 1, parts of the structure having been broken. away to reveal internal details;

Fig. 3 is. an enlarged view in left side elevation of the improved mixer shown on the truck in. Fig. 1;

Fig. 4 is a view in rear elevation of the mixer shown in side elevation in Fig. 3; and,

Fig. 5 is a view in front elevation of. the mixer illustrating particularly the water tank mounting arrangement.

Referring more particularly tothedrawings. and especially to Figs. 1 and 3 thereof, the mobile concrete mixer there shown as an exemplifyingembodiment of the present invention constitutes an improvement upon theusual truck mounted or transit-mixer of well-known construction. As shown, the improved. mixer comprises essentially a large, relatively long tapered mixing drum of novel shape that isrotatably mounted in a rectangular box-like supporting frame 11, the arrangement being such that the entire apparatusis especially adapted for mounting on the chassis of a standard commercial motor truck T with the axis 12 of the drum 10. disposed longitudinally of the truck and inclined upwardly toward the rear thereof.

As best shown diagrammatically in Fig. 1, the particular motor truck T of standard. or conventional. constructionthat is represented in the drawing, isof the type having side frames Smounted, onv two front; wheels F for steering and four rear wheels R1 arranged as a bogie in.

tandem axle relationship for. driving, although it is to be understood that the mobile mixer. ofr the present invention may be utilized with similar, advantages ontrucks ofdifferent construction having, for, example, only two rear wheels. Furthermore, the standard truck T shown is of the type having the drivers cab C disposed behind the propulsion engine E. Because of the fact that trucks of this general type are mass-producedby variouszmanufacturers in competitive sizes theyv constituteamost. economical form of transportation for any suitable load such as a transit mixer.

As a specific example, but not to be taken as a limitation upon the scope of: the invention, the particular standard truck T represented inthe drawing may be assumed to have a wheelbase of. 193' inchesand the total weight of its chassis is. 12,250 lbs. With the chassis weightassumed as concentrated at a point. G represent ing the center of gravity of the truck structure, the weight of the chassis. is so divided between. the wheels of the truck that the rear wheels R support 6,700 lbs. andithe front wheelsF support 5,550 lbs. According to previous practice, when aconcretemixer. was loadedin the usual manner on a truck of this type, approximately ninety percent of the added load was. ordinarily carried on the rear wheels R. This concentration of loadon the rear wheels occurred because of the fact. that previously used truck mixers were provided with mixing drums of such shape as to require mounting them .rearwardly and largely over the rear wheelsin order that the discharge end of the mixer might be above the rear endrof the truck frame to facilitate discharging concrete at'the back of the truck. Under these circumstancesonly about ten percent of the combined weight of the. mixer and-its loadof concrete was carried by the front wheels ofthe truck.

A truck of the conventionaltype represented by the diagrammatically illustrated standard truck T isof such length and design as to enable it.to carry. on certain highways, for instance, a permissible total overall weight of 46,400 lbs., divided in such a manner'that no more than 32,000 lbs. are imposed upon the highway by the rear wheel bogie nor more than 14,400 lbs. by the front wheels Allowing for the weight of thetruck'chassis itself, this truck is therefore capableofcarrying a load that may impose as much as 25,300 lbs. additional-weight on-the rear wheel bogie and 8,850 lbs. additional on-thefront wheels, without exceeding the wheel load-limits that-have been established as the maximum permissible for use on these public highways. With previously usedtransit mixers having drums of shape to concentrate the load over the rear wheels of trucks of thistype, the total wheel loading of 32,000 lbs. on the rear wheels was-attained with a load of approximately 4 /2 to a maximumof 5 cubic yards of concrete in themixer drum.

Inthe improved transitmixer-constructed in accord- 4 ance with the present invention, the load of concrete is disposed forwardly-'onthe truck to effect abetter distribution of the total load between the rear wheels and the front wheels of the truck; As shown in Fig. l, the combined weight of the improved mixer and its load of concrete may be assumed to be concentrated approximately at a point 13 representing the center of gravity of h loa ed. mixer, under normal conditions with the drum stationary and the concrete in fluid condition of normal consistency. In thisparticular instance, and by reason of the improved construction, the center of gravity 13 is positioned about fifty inches forward of the load center of the rear wheel bogie. With the center of gravity 13 inthisforward position and the mixer loaded to predetermined capacity to impose the permitted additional weight of=i25g300 lbs..on the rear wheels R, there is also imposed a proportionate additional weight of 8,850 lbs. on the front wheels F, thereby bringing the total front wheel loading up. to theallowable maximum. of 14,400 lbs. Under these circumstances, the front wheels carry some twenty-six. percent. of the weight of the loaded.

mixer. By this improvedarrangementof the mixer structurewhereby proper distributionof the load is achieved, the truck is enabled tozcarry. its total allowable maximum usefulload of 34,150 lbs. without subjecting the roadway to excessive wheel loads. Through optimum loading of all of the wheelsv of the truck in this manner, this particular standard truck. T is. capable of. carrying, in addition tothe weightof themixer, about 6% cubic yards of concrete. This constitutes anincreasein the permissible load of .concreteof substantially. thirty toforty percent over that .previouslycarried on trucks of. similar characteristics .in truck-mounted mixers of previously known design.

The new and improveduresults achieved. by the invention have been .set forth.with.respectr to a particular type and size of standard commercial. motor truckv purely by way of illustration. It is .to be understoodthat trucks of other sizes and styles may be;-utilized with mixers designed inaccordance withrthe-principles of the invention, perhaps to meet somewhattdifferent particular load limitations, inan equally eifectivemanner to achieve optimumwheelloading and maximum load carrying capacity. Furthermore, .as. improvementsare made in highways and in the design ofcommercialtrucks, particularly with respect to the load+carrying and steering capabilities of their front wheels,.the.invention will makepossible still greater. economiesinthe. transportation of concrete to construction sites.

The term standard commercial motor truck'as used in this specification is intended torefer to trucks of the type having the cab behindtheengineas shown in the drawings. Other. trucks provided withspecial cabs or of the type having the cab. mounted 'overythe engine involve additional expense bothin first:cost.and in cost of-operation and they, are not considered standard or conventional in the sense ofproviding the most. economical form of transportation. However, whenthe improved mixer is used with trucks of thecab-ovenengine' or similar special type, the advantages of the presentinvention persist and may be realized-to antevenrgreater degree.

As appears .in Fig. l of'the drawings, disposition of the weight of the mixer and its loadforwardly on the truck T: occurs because of the shape-of the'mixing drum 10 being such that the. loadofconcreteis :carriedlargely in the forward. end' of the drum and'also from the fact that the drum itself: is positioned forwardly on the truck. In this respect it should be'observed that mixer drums necessarily must be made considerably larger than the volume. of concrete to-.b.e, mixed in order that mixing space may be; available,.andi also: that; certain overall dimensions mustbe-;observediinrorderrthat the-truck and its load will have adequate-clearance-on the roads.

As best shown in Figs. 1 and 3 the tapered drum 10 comprises mainly a body. portion 14 that is'preferably of generally coniform orfrusto-conical shape, although the shape. may vary somewhatfrom that of;a true'cone. The drum 10. is disposed longitudinally-ofthe. truck T. with the large endofthe conicalbody 14.positi0ned forwardly and closed by a domelikeheadjlS-toconstitute a mixing chamber or compartment. As shown, the large end or head 15 forming the closed is disposed, close to' the back of the truck cab C and as low as practicableinrelation'tdthe-side frames 8' of the truck, thema-x-imumoia-meter of the drum being'such end 'of the tapered drum 10.

. in the particular structure that its outer edges come within the clearance limits of the truck height and width. The longitudinal geometric axis 12 of the conical drum is inclined upwardly and rearwardly at an angle of about 11 degrees to the plane of the frame S, the drum body 14 being of such length that its small end presents an elevated discharge opening 16 disposed above and in substantial vertical alignment with the rear edge of the rear pair of wheels R.

By this arrangement, the discharge opening 16 is disposed as high as desirable and conveniently positioned at the back of the truck T to facilitate spouting the discharged concrete at the site of placement while at the same time the closed large end of the drum is positioned as far forward as possible closely adjacent to the truck cab. The shape and degree of taper of the drum body 14 is-such that its upper element is disposed substantially horizontally or nearly parallel with the plane of the truck bed or side frames S as appears in Fig. 1. The particular mixing drum 10 shown in the drawings as a specific example may be about 146" in length as measured along the axis 12 from the center of the head 15 to the plane of the discharge opening 16. The frusto-conical body portion-14 is about 111" long and constitutes approximately seventy-five percent of the total length of the drum. The small end of the drum constituting the elevated discharge opening 16 is about 34" in diameter and the large end of the conical body 14 is about 84" in diameter, this being the largest diameter of the drum. The angle of the slope or the angle of inclination of the conical wall of the drum body 14 to the axis 12 is not over about 12 /2 degrees. The ratio of overall length of the drum 10 to its greatest diameter is in this instance of the order of 1.75.

That the dimensions and proportions of the exemplary drum as set out above are material departures from established truck mixer practice will be realized when one considers that according to established practices, the taper of the discharge cone of an inclined axis drum was generally of the order of twenty degrees, the angle of axisinclination to the horizontal was substantially in the range of 15 degrees to twenty degrees, and the ratio of the length of the discharge cone section to the greatest drum diameter was substantially less than 1.5. These dimensions were dictated by the requirements imposed by the conventional disposition of the drum-driving mechanism and water supply tank between the mixing drum and the cab of the truck, so that in order to have adequate space for mixing at the forward, closed end of the drum, and adequate height for discharging the concrete a much shorter and relatively wider drum was employed, and it was set on an axis of much steeper inclination. In these drums, the length of the cone was generally of the order of not to exceed two-thirds of the total drum length and in some instances was even less.

By reason of the long tapered shape and inclined position of the present drum 10, load of concrete in the drum tends to move downward and forward, and accumulates in the lower part of the enlarged closed front end or head of the drum, thereby disposing the center of gravity of the load forwardly in the drum. This coupled with the fact that the drum itself is disposed forwardly on the truck frame positions the load in such a manner that some twenty to thirty percent of the weight of the loaded mixer is carried by the front wheels of the truck. As previously mentioned, illustrated, the center of gravity 13 of the loaded mixer is so positioned that about twentysix percent of the load is carried by the front wheels, the center of gravity 13 being positioned about 50 inches ahead of the load center of the rear wheel bogie. Since the wheel base of the particular truck T shown in the drawing is 193 inches, the ratio of the distance by which the center of gravity is ahead of the bogie center, to the wheel base is .26, or that is, the center of gravity 13 is a little more than one-fourth the length of the wheel base ahead of the bogie center.

'A simple method of determining the load which the mixer imposes on the rear wheels of the truck T when it is on level ground is expressed by the formula where RA is the a large proportion of the -of the mixer frame 11,

this equation expresses the static balance between the two moments of force around the trucks front axle. According to this formula, TL (the load that can be carried without exceeding the maximum permissible weight on the rear wheels) for a given wheel base truck is inversely proportional to the distance from the front wheels to the center of gravity 13 of the truck mixer. Part of this distance is occupied by the truck (its engine and cab) and will vary of course for different trucks. But regardless of this dimension, the balance, which may be referred to as the G dimension, from the back of the truck cab to the mixer center of gravity, is critical in determining the portion of the load imposed on the front wheels of the truck. The lower the G dimension, portion of the load on the front Wheels.

Another critical dimension is the horizontal distance from the back of the truck cab, or rather from the front end of the mixer frame arranged closest to the cab (assuming only a very slight clearance is required) to the bottom of the discharge opening at the elevated end of the drum. It is from this latter point that the mixed concrete has to be spouted or discharged into receiving means. This dimension may be referred to as the L dimension. Increasing the L dimension increases the capacity of the mixing drum. Furthermore, if the L dimension is too short for a given truck, the discharge end of the drum may be ahead of the rear wheels of the truck, making it impractical to discharge laterally by the chute 30 or vertically (when the chute is removed) into a receiving hopper or buggy. The greater the L dimension, within practical limits, the less danger there is of having too short a mixer for adequate discharging purposes.

If these two dimensions are expressed by the ratio G/ L, the lower the ratio is, within practical limits, the more advantageous the design will be, not only because weight will be distributed forward but adequate over-all length as well as mixing capacity will be obtained. The mixer of this invention represents a decided advance in the art, for the disposition of the drum 16 at the forward end where it may be mounted closely adjacent the cab C of the truck and the shape of the drum as herein set forth, greatly reduces the G dimension, while the length of the drum on its inclined axis provides a substantial L dimension. In the embodiment of the invention illustrated hereby, the ratio G/L is less than .45 and of the order of .40, which is a substantial departure from prior art machines in which a ratio of not less than about .50 was obtainable.

In order that the G dimension may be uniformly determined, values here given are based on the determination of the center of gravity with the drum loaded to its rated capacity according to NRMCA (National Ready Mixed Concrete Association) standards; concrete fully mixed and of adequate slump (approximately five inches) so that the concrete does not build up unduly in certain areas of the drum; drum not turning; truck on level ground; and suflicient water in the water tank 38 to provide customary flushing of the drum when it is driven back to the loading plant after discharging its mixed concrete.

In order that the drum 10 may be rotated about its inclined longitudinal axis 12 in mixing or discharging concrete, the drum is provided at its forward end with a trunnion 17 that constitutes a journal projecting axially from the center of the head 15. The trunnion or journal 1"] is rotatably received Within a bearing 18 (which is preferably self-aligning), that is carried by an upstanding forward frame member 19 constituting the front part of the mixer frame 11 and positioned closely adjacent to the back of the truck cab C. The elevated discharge end 16 of the drum 10 is likewise rotatably supported by a rear frame member 21 that also constitutes part of the mixer frame 11 and is upstanding at the rear of the truck. As best shown in Fig. 4, the rear frame member 21 carries a pair of spaced rotatably mounted drum supporting rollers 22 arranged to rotatably engage the respective lower quadrants of a ring or trackway 23 that encircles and is secured to the tapered body 14 of the drum 10 near its small end. The trackway 23 constitutes a rear journal that is disposed in axial alignment with the forward journal or trunnion 17 in rotatably supporting the drum at its respective ends to provide for turning it upon its inclined longitudinal axis 12. Since by reason of the inclination of the axis 12 the entire drum 10 has a tendency to slide forward, the front or mam bearing 18 in the greater is the prosmegma theforwardframe member; 19 is; preferably." selfialigningzand; of. well-known: anti-friction type. adapted. to: resist. thrust. loads as: well. as radialloads.

As; appears; Figs. 4: and 5, the: lower-"part of: the mixerframe 11..is. constituted. by 'aapaii: of spaced. parallel; side: frame. elements 24- that'. are: arranged. respectively to: restuponand be securedto: the. sideframesS. of the truck. chassis. As. shown.v in Fig; 4,-. the: rearframe: memberv 21. comprises spaced vertically disposed s'det'pieces or. uprights 25- that. are secured at their; loweruend'srto. the ends. of therespective. side: frame: members 24. and are. connected near. the. midpoints; by. a transversemember: 2.6 i which carries the rollers 22 thatirotatably support. the. rear end: of the drum.10. Alighterrtransverser member: 27 is connected between the rear. side: piecesli: in. the. region of the axisof the drum: a and serves; to; carry a changing-..hopper 28.? throughwhich materialsuch as; concrete aggregates may befed; into the drum. through the. rear opening 16: for mixing: therein. Beneath the charge ing hopper 28; the; rear side piecesxor uprights; support a gathering chute or. collection. hopper 29 which operates. during unloading of the: drum: to receive-the discharged concrete. and. channel itinto distributing apparatus. such. as a. movable. distributing: chute or spout 30: that1is. pivotally supported. on a. spout pivoti3l atxthe rear of'the frame. 11 asshown in Fig. 3.

As best shown in Fig. 5 the. frontframemember. 19 is. constituted by a pair of upstanding: side pieces: or uprights. 34that. are secured at their. respective. lower. ends. to the: forward ends of. the sideflframes'. 24' andare interconnected: near their upper ends by a transverse. member 35 that carries: the main bearing 18. The front. frame member. 19 also. carries a water supply tank 38 that. is disposed transversely off the: frame 11. ahead ofv the forward end of the drum-10 in a position to overhang the top of the drivers cab C as. shown. in'Figs. l and 3-. With the Water tank 38 disposed inthis over.- hanging position,. ,it is arranged to offer no interference. to positioning the. drum 10 as:far. forwardly on the truck as may be. desired. Furthermore, withthe tank 38' overhanging: the cab C as. shown, its'weight iszlikewise disposedv forwardly on the. truck in accordance: with. the principle of proper distribution of the weight-among the wheels. of the truck.

Referring to.Figs. 2 and..'5, it. will. be: seen that; the water tank. 38 is of rectangular shape. and is carried primarily by a transverse, tubular, torque-resisting element. 39 that is rigidly secured to and extendsoutwardly from. the upper ends of the frontside pieces 34 at eachside of the from frame member 19.. Near'its respective outer ends, the. tubular transverse. tank supportingrmember 39 is. provided with a pair. of angle: brackets 40 each having: two divergent. arms extending: upwardly and for:- wardly in a manner'to engage. and support the back. andv bottom of the respective ends. of. the: rectangular water. tank 38.v As bestshownin. Fig: l the; upper end. of. each. bracket 40. is. connected. to the. forward end: of an upper. tie piece or: top frame element 41-, the. twotie-.pieceszextendingrrearwardly along the. top of: the-drum. 10 at the respective sides thereof and being connected: at. the. rear: to' the. upper ends of the respective rear; side pieces. or uprights 25. The uppertie pieces 41,. being.- disposed parallel to the lowerframe. side pieces: 24;. con-' stitute with them and the front: and rear/vertical frame members a substantially rectangular box-like frame: structure' about the mixing: drum 10;

Power for rotating. the: drum 10in mixing-or discharg in concrete maybe derivedv either from. the propulsion engine E of the: truck. through the usual power takeofi: connection or from a separate. mixer driving'engine; In: either event the power transmitting'apparatus is, in ac.- cordance. with the present invention,v mounted on the mixer frame l'lbeneath the elevated discharge end of: the: drum 10. By this arrangement the power'transmitting mechanism is so disposed'as not to'interfere'in anyway with. positioning the drum. 10 as; far: forwardly" asmay be desired on the chassisof' the truck E.

In the particular. exemplary. construction shownsinithe drawings, the drum driving mechanismis represented by aseparatemixer driving engine. 45: and its associated power transmission mechanism or gear 'case: 46'. As; shown, the engineand power transmission:mechanismzare joined to constitute. a unitaryxstructure: that is mounted? on a' sub-frame 47 disposed. transversely of the-sides frames 24? and secured! thereto just. ahead of thetrearr 85:

. tion as selected;

frame; member" 21'.

a. vertically positioned. hand transmission. mechanism. by 49 on the outer: end. of.:a;

witlr tlie:rotationaL axis; 12L of the drum- 10. A complementary sprocket; 50- ofv thev ring: type is.

disposed. to. en-

circle and is.-secured1;on=.the tapered body 14 of. the drum.

10; just forward of. the;.bearing ring. 23;.and in cooperating: alignment with; mechanism. A power transmitting chain. 51. encircles the. drum. 10: in engagement with the sprocket 50 and. passesaround thewtransmission. sprocket 49 as shown in. sprockets. for transmitting,

Fig.. 4 to interconnect the; powento' rotate the drunr.

Ittwill be observed. that with. the three-point mounting for; the drum. as-shown; i..e. with the front .end supported by' the axial bearingl8 andtthe elevated end by the I'Oll: ers.22.in-r=which.the drumis cradled, twisting and weavingof. thetruck frame occasioned. bytravel of the truck.

mixers,. in considerable misalignment in the power trans? mitting; train. between. the. relatively fixed power source on the frame: and.- the angularly moving forward end of the drum to which: the power. was transmitted. By applying the: driving; power to the elevated discharge end. ofthedrum, movementof the drum occasioned by the twisting. and weaving; a. minimum of misalignment between. the axis of the drum and: the axis of the. transmission mechanism 46 ment of.-the. frame.

The inner: surface of the drum 10 is provided with helicalmixing blades. 53, partly shown in Fig. 4, that function to. tumble. and propel the concrete during mixing or discharging thereof. In the particular mechanism hereshown, the hand leverv 48 is arranged to have a central neutral positionin-which the transmission mechanism istdisengagedso that no power is transmitted tov the-.drum.. When. the lever 48 is moved in the one or theuother direction from the. drive-mechanismis engagedto effect rotation of the drumv 10.-in. the: corresponding forwardor reverse direc- In. the particular. arrangement shown, 53' are. soarranged that when the drum follows the twisting movethemixing blades is. rotated: in. one fed inwardly and of the drum 10.. to. the. other position to reverse the direction of rotationofQthe drum, the'helicall blades 53' propel the mixed concrete upwardly. and outwardly along the tapered 'drum body. 14to.'discharge it through the discharging opening 16' into the. collection hopper 29. Under other'cirmixed by the blades in the forward end cumstances, the mixingapparatus may be so arranged thatthe. mixingaction occurs while. the drum is rotating. in the direction. to. discharge the concrete, the dischargeopening l6'then beingclosed duringthe mixing. operation by a. suitable. removable cover or the like of' well-known.construction,v the. details of which need not be setforth. herein. The. speedlofrotation of the drum for mixing or dischargingtis.establishedby adjusting the speed. of operation. of-theengine 45', a. throttle control lever. 55'. being providedv for that. purpose. on the left side..- of the. machine near. the. directional control hand levera48; The. engine 45and associated-mechanism is protected-by antenclosing metalhousing-56 and thechain and. sprocket drive is enclosed by, asuitable chain guard housing. 57..

The water tank 38 is preferably of: the two-compartment type, one. compartment containing water. for

introduction into the concrete during mixing and the.

other containingwater for flushing out'the mixer drum after discharging the concrete. A dual control valve 61 is connected as shown 'in'Fig. 5 to the respective compartmentss'oftthe tank 3.8 and.is arranged .to connect either compartmentselectivelv with a water pipe or conduit 62. The pipe- 62 extends. and then-back along;

The. power transmitting: mechanisnr 46. is: of:v the. sel'ective',.- reversing; clutch type. controlled. by. lever 48. that. extends from; the-:gear: case in: an: accessible; position: at the left. rear." corner of the -frame:.11';. Power. istransmitted. from the means. of a. sprocket. wheel. shaft; extending from: the. transmission .gear: case 46!.With'; its. axis. disposed parallel the: sprocket 49' on. the transmission.

of the. truck frame results in:

drivingsprocket 49, since the the central neutral position,v

direction the concreteaggregates are.

When. the control lever 48 is moved across the: front ofthe drum.- 10 the=right side: thereof to awater. pumpr 63. thatiis dlSp0Se adjacentto andis .operatively connected to be driven for mounting longitudinally on by the engine 45. From the pump 63 a return pipe 64 leads back along the drum to a water inlet connection 65 that projects axially through the trunnion 17 into the interior of the drum 10, being provided within the drum with a nozzle of the usual type for injecting water into the concrete mix as the drum is rotated during the mixing operation.

By disposing the Water tank over the cab of the truck and arranging the drive mechanism, as set forth, beneath the elevated end of the drum, the space that these essential elements formerly occupied between the drum and the cab 'has been madeavailable for utilization by the mixing drum so that the latter, being lengthe ned, can be set at an appreciably less angle of inclination without sacrificing discharge height or maximum diameter for effective mixing. As a result, greater drum capacity is provided, as well as improved discharging ability.

From the foregoing description and explanation of the operation of the exemplary transit-mixer set forth herein it will be apparent that the truck-mounted mixer embodying the present invention is capable of carrying the maximum load of concrete that can be transported by a standard motor truck without causing any wheel of the truck to impose an excessive load on the roadway being traversed.

Although a single mixer structure illustrative of the present invention has beenset forth in detail herein by way of a full disclosure of a practical and useful embodiment of the invention, it is to be understood that various other arrangements and different proportional relationships of the elements of the apparatus maybe utilized without departing from the spirit and scope of the invention as defined in the subjoined claims.

An exemplary embodiment of the invention having now been fully described, I claim as my invention:

1 In a truck mounted mixer adapted for economical use in conjunction with a motor truck of conventional construction having the drivers cab disposed behind the truck engine, a long tapered mixing drum arranged the truck for rotation upon its ax1s with its large end closed forming a mixing chamber of large diameter disposed closely adjathe back of the truck cab and with its axis inclined upwardly and rearwardly in fixed position relative to the truck to present its open discharge end in the usual elevated position approximately above the rear edge of the rear truck wheels, said drum being of substantially frusto-conical shape with the ratio of its length to its greatest diameter substantially in excess of one and one-half to one, the shape and position of said drum being such that the weight of the drum and its load is distributed among the wheels of the truck in such a manner that twenty to thirty percent thereof is carried by the front wheels of the truck, whereby optimum distribution of the load on the truck wheels is effected to provide for carrying upwards of six cubic yards of concrete in said mixing drum without imposing in excess of 32,000 pounds on the rear wheels of the truck.

2. In a transit mixer adapted for mounting on a conventional motor truck of the type having the drivers cab mounted behind the propulsion engine, a long rotatable mixing drum having a fnlsto-conical body portion tapering at not more than fifteen degrees throughout in excess of two-thirds of the total drum length and having a dome-like head closing the large end thereof to constitute a mixing chamber of large diameter, 'said mixing drum presenting a discharge opening at its small en adapted to be disposed in elevated position above the rear of the truck as is usual for convenient discharging of mixed concrete and being of such length that its large closed mixing end may be disposed closely adjacent to the back of the drivers cab, whereby concrete carried in said drum tends to be concentrated in the large forward end thereof during mixing and transportation to dispose the center of gravity of the loaded mixer substantially forward of the mid-point between the rear of the truck cab and the discharge opening at the end of the drum.

3. In a truck mounted transit-mixer for use on a motor truck of standard construction, a supporting frame adapted to be mounted on the truck chassis, a relatively long mixing drum arranged on said frame in a manner to extend from a position directly behind the cab of the truck'rearwardly and upwardly to a position above the rear of the truck, power transmitting mechanism for driving said mixing drum disposed on said frame beneath and operatively connected to the upwardly extending end of said drum, and a water supply tank mounted on said frame forwardly of the forward end of said mixing drum in position to be disposed above and overhang the cab of the truck and operatively connected to furnish water to said drum, the arrangement being such that said water supply tank constitutes an integral part of the transitmixer structure that is separable from the truck as a unit yet said tank is disposed in a position which does not interfere with said mixing drum being mounted directly behind the cab of the truck.

4. In a concrete mixer for mounting on a standard motor truck of the type having the operators cab on the bed behind the engine, an open-ended mixing drum of generally frusto-conical shape having a closed dome-like head at its larger 'end and of length such that when mounted as hereinafter specified, the center of gravity of the loaded mixer is substantially forward of the midpoint between the back of the truck cab and the small end of the drum, said drum being mounted for rotation upon its longitudinal geometrical axis with its closed large end arranged for mixing concrete and disposed adjacent to the cab of the truck and with its upper longitudinal element disposed approximately parallel with the plane of the truck bed to present its open small end in elevated position above the rear wheels of the truck for discharging mixed concrete, and power driving mechanism disposed between the elevated small end of said drum and the frame and operatively connected to said drum for rotating it.

5. In a truck mounted, transit concrete mixer adapted for mounting on a conventional motor truck, a supporting frame arranged to be mounted on the truck chassis, a relatively long, generally tapered mixing drum rotatably mounted on 'said frame with itsaxis of rotation fixedly inclined to the plane of the truck chassis at a relatively low angle of inclination such that the larger forward end which is closed provides a mixing chamber of maximum diameter ample for adequate mixing and closely contiguous to the forward end of the supporting frame and the back of the cab of the truck when the mixer is mounted thereon while the elevated end of the drum which is open provides a discharge opening at the usual height for Wide spouting range, and the length of said drum being substantially greater than its maximum diameter, the arrangement being such that when the mixer is mounted directly behind the cab of the truck the ratio G/L is less than .45, where G is the horizontal distance from the back of the cab to the center of gravity of the loaded mixer and L is the horizontal distance from the back of the cab to the discharge opening.

6. Apparatus as set forth in claim 5, wherein the angle of drum inclination is substantially less than 15 degrees, the ratio of drum length to maximum drum diameter is of order of at least 1.5 to l, and the tapered portion is substantially in excess of two thirds of the length of drum.

7. A concrete mixer adapted for mounting on a conventional motor truck of relatively short wheel base for easy maneuverability, said mixer comprising a frame "including members substantially co-extensive with the portion of the truck chassis in back of the drivers cab and securable thereto, a separate drum-rotating engine arranged transversely at the rear of said frame, a rotatable, internally-bladed mixing drum longitudinally mounted on said frame having its axis of rotation inclined to the bed of the truck and its forward end closed and disposed above the forward end of said frame members, said drum having a generally frusto-conical discharge portion tapering inwardly toward an elevated discharge opening disposed rearwardly of said motor, the inclination and taper of said drum affording clearance beneath the drum and above said motor, and insuring when the drum is mounted closely adjacent to the rear of the truck cab that the center of gravity of the drum when carrying its rated load of concrete is substantially forward of the point of wheel mounting support at the rear of the truck, and power transmitting means interconnecting the motor and the drum to produce rotat'on of the drum.

.8. In a transit-mixer especially adapted for mounting -be mounted -with the 1 1 on the chassis of a. motor truck of the usual commercial type having the driverls cab behind the propulsion. engine; an internally-bladed mixing drum oftapering shape .arranged for mounting longitudinally ofwthe motor-truck on an inclined axis with its small :endopen and in elevated :position at the rear of the truck to constitute a discharge opening, and with its rlarge end closed to constitute a mixing chamber; a framerdisposed to support said drum for rotation'about its inclined longitudinal axis and adapted to 'be secured to the truck chassis in :a manner to maintain said :drum in position 'on the truck with its forward end closely adjacent the :cab sof'the'truck; :power transmitting mechanism mountedon said frame adjacent the elevated discharge :end of said drum and operatively connected to said drum in a manner 'toefiect 5 rotation of said drum-in *either direction selectively for mixing and discharging concrete, the tapervand-inclination of the :drum being such that the weight 'of :the concrete mixed and transported-"bysaid :drum- 'is. disposed;forwardly on said frame so that'the ratio of G/ L, where G is the horizontal distance from the back of the truck cab to the :center'of gravity of thewloaded mixer 'and L is the horizontal distance from the back :of the cab to the lower .end of the discharge opening is not iILEXCBSS'zOf .45, whereby a maximum IIOHdlOfX-COIICI'CtG :may be transported without imposing excessive iwhee'l .loads 'on .the highway being traversed.

9. A truck-mountable concrete mixer :capablezof mixing and hauling a larger batch of concrete fthan heretofore possible without imposing in 'excess of'a predetermined load on the rear wheels 'of the truck, .said mixer comprising a frame arranged for mounting on the bed of the truck 'behind :its 'cab, an internally-bladed, :rotatable mixing drum journalled on said frame 'with its axis of rotation inclined upwardly toward the :rear :of the frame 'at-a fixed angleto'the :plane of theitruckJbed, said drum'having its forward end closed by 'a dome-likerhead of large diameter providing =ample free-mixing :space above the materials constituting :such .a batch,-.the ele- 'vated end of said drum being open to permit charging and discharging, and the :sides 50f said drum itapering inwardly from ,said dome-like ihead toysa'id charging and discharging opening, said Idrum being iof 'a :length ,at least as great as said frame and having its tforward'end at the forward endo'f the :frame iwhereby'thezmixer may head of .the drum 'rclosely behind the cab of the truck, the length-of said drurnproviding that the, discharge opening is .at the usualhigh and rearwardly disposed elevation'ifor :wide spouting ran'ge, and

means for rotating the drum including .a ipower trans- 5;"

mission mounted :on the frame "adjacent the-:tapered portion of the :drum, the entiregarrangement'being rsuchzthat the center of gravity of .the mixer when transporting such a batch is siifiiclently forward 'of the mid-point forward end at theforwardend of ddrum providing,

.12 between :the =rear-ofthe truck cabsand the open end of the drum to impose not in excess of the predetermined ipermissible load on the rear wheels of the truck.

10. A truck-mountable concrete mixer capable of mixing and hauling a larger batch of concrete than heretofore possible without imposing .in excess of a predetermined lload on .therear-wheels of the truck, said mixer comprising a frame arranged for mounting on the bed -of the truck behind .its cab, an internally-bladed, rotat- ,ample free-mixing spacez above the materials constitutingsuch a -batch,.the elevated end .of said drum being open to; permit charging and discharging-and the sides of said drum tapering inwardly tosaidopening over atleast two-thirds of the length of the drum, said drum being of a lengthat least as ,greaL-as said frame and having its the frame whereby the mixer may be mounted with the head of the :drum closely behind-thev cab'of the truck, the length 'of :said

,despite. the low angle of the drum inclination, that .thedischarge opening is; at the usual high elevation .for wide spouting range, and means for rotating the drum including a power transmission mounted on "the frame ::between the tapered portion of the drum and the frame, the entire arrangement being such that the center of gravity of the mixer :when trans- ,porting .such -,a batch is sufficiently forward of the midpoint,between-theirear of the truck -cab and the open end :of the drumntoqimpose not in excess of the predeterzminedpennissibleload on therear wheels 'of the truck.

References .Cited in the .-file of this patent UNITED STATES PATENTS Number Name Date 703,424 Judd July .1, 1902 1,781,965 Ball Nov. 118, 1930 1,872,624 .Eggert Aug. -16, 1932 1,901,305 Knowles Mar. 14, 193-3 .1,919,073 Paris July 18, 1933 2,013,359 v Paris :Sept. .3, 1935 2,018,112 .Ball Oct. 2-2, 1935 2,338,820 Peters Jan. '11, 1944 ;.2,487,.,-887 McEachran Nov. .15, .1949 2,538,871 Jedlicka Jan..23, 1951 FOREIGN PATENTS Number Country Date 546,329 Germany Mar. 1 4, 1932 

